Cartilage tissue is a component of the nose, ears and joints. Cartilage tissue is composed of chondrocytes and a specific extracellular matrix that contains type II, IX, and XI collagens and proteoglycans, but not type I collagen. Cartilage tissue damaged by joint injury etc. does not spontaneously heal itself, and the damage will deteriorate without repair treatment such as transplantation. For transplantation, however, cartilage tissue to be transplanted into the damaged site needs to be obtained. Transplantation of the patient's own cartilage from other body parts inevitably results in lack of cartilage tissue in these parts, and therefore, the size of the damage site that can be treated by transplantation is limited. Another current approach is transplantation of the expansion culture product of harvested chondrocytes, but chondrocytes may be transformed into fibroblastic cells during in vitro culture and this approach cannot produce a sufficient therapeutic effect (Non Patent Literature 1). Yet another proposed treatment is administration of mesenchymal stem cells. However, mesenchymal stem cells can differentiate into multiple types of cells, and the administration inevitably results in transplantation of not only chondrocytes but also undesirable tissues, such as fibrous tissue expressing type I collagen and hypertrophic tissue expressing type X collagen (Non Patent Literature 2).
Currently proposed is repair treatment using chondrocytes induced from pluripotent stem cells, such as iPS and ES cells (Non Patent Literature 3 to 7). However, the use of pluripotent stem cells has produced several problems, including the formation of fibrocartilage and teratoma. Therefore, there is a need for the development of a method for driving pluripotent stem cells to generate high-quality cartilage tissue without in vivo cancer formation.